Poster A34, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Frontoparietal neurostimulation alters the theta-gamma neural code for working memory
Marian Berryhill1, Elizabeth Johnson2, Adelle Cerreta1, Dwight Peterson3, Kevin Jones4; 1University of Nevada, Reno, 2University of California, Berkeley, 3Concordia College, 4Colorado State University
There is considerable interest in maintaining or enhancing working memory (WM), the neurocognitive horsepower associated with ecologically valid measures of cognitive performance. However, despite its importance, research and commercial interventions attempting to increase WM capacity provide mixed results. One emerging approach is to couple WM training with transcranial direct current stimulation (tDCS) to expedite and enhance behavioral training gains, presumably via reinforced neuroplasticity. In the current study, healthy young adults were trained and assessed on a difficult visuospatial WM task over one week, with sham or active tDCS. The high-density electroencephalogram (EEG) was recorded prior to tDCS, and again after completing the training + tDCS program. Participants who received active anodal frontoparietal tDCS demonstrated significant behavioral improvement on the WM task, unlike those who received sham stimulation paired with the same WM training. To elucidate the neural mechanisms behind observed training gains, EEG data were spatially-filtered using the Laplacian transformation, and analyzed for event-related potentials (ERPs), power spectral density, and cross-frequency coupling between theta oscillations and broadband gamma activity (i.e., theta-gamma PAC, considered a “neural code” for WM). Outputs were tested using a Monte Carlo method with cluster-based multiple comparisons correction. Importantly, tDCS changed the profile of frontal theta-gamma PAC and induced frontoparietal voltage shifts in contralateral ERPs. Because WM training alone did not influence WM or the EEG, these findings demonstrate that tDCS altered the theta-gamma neural code.
Topic Area: EXECUTIVE PROCESSES: Working memory